UK patent specification 2,115,040 discloses a wellbore screen. This screen may include outer and/or inner protective layers which are co-axial to the filter layer and which have a much larger sieve opening size than the filter layer or layers.
A problem encountered with the screen of UK patent specification '040 is that woven metal wire and other filter sheets are fragile and can be easily squeezed and damaged during installation and use. Only a minor deformation of the filter sheet may already result in variation of the sieve opening which may hamper a proper performance of the screen.
Furthermore sand screens of the known type are typically made in a flat or tubular shape and are designed to remain in their original shape without substantial deformation during and/or after installation. However, in boreholes with an irregular surface and/or sharp bends this requires the use of a screen with a much smaller diameter than that of the wellbore. Such use of a small diameter screen will result in high fluid flowrates through the sieve openings of the screen, strong wear of the screen and an increased risk of plugging of the screen and of collapse of the borehole.
It is an object of the invention to alleviate the problems.